The Chelsea chairman, Bruce Buck, has attacked a minority element of the club's support for anti-semitic abuse of the new manager, Avram Grant.

The Israeli's appointment after Jose Mourinho's departure from Stamford Bridge has provoked strong feeling but Buck said some of the comment which the club had received crossed the boundaries of acceptability.

"We welcome all constructive points of view," Buck wrote in Saturday's match programme for the visit of Fulham. "But there have been a few which could be viewed as racist and anti-semitic and that must stop immediately. This is one thing we will not tolerate whether in written correspondence, on the chat pages, on posters or banners or through singing and chanting. And it unfairly smears the reputation of the vast majority of Chelsea fans who rightly do not want to be associated with such activity."

Grant, the former Israel coach, who arrived at Chelsea over the summer as director of football, will not allow any slurs to deflect him from his purpose. He faces a huge test on Wednesday night in the Champions League at Valencia and already, after only three games, the problems are mounting.

He lost his first match 2-0 at Manchester United and although his team won 4-0 at Hull City in the Carling Cup, Saturday's 0-0 draw against Fulham extended an alarming sequence. Chelsea have gone four Premier League matches without a goal, have made their worst start in seven years - the season when Gianluca Vialli was sacked in September - and are seven points behind the leaders, Arsenal.

There is dissent, too, from within the ranks. Grant's appointment has not been met with universal approval from the players, many of whom do not respect his achievements or enjoy his training, and Steve Clarke, the assistant manager, is poised to quit.

Clarke, who was Mourinho's right-hand man, was upset by the manner of the Portuguese's departure. He has been considering his position and, mindful that Grant intends to bring in his own backroom staff during the international break, which begins next week, is ready to call time on his lengthy association with the club after Sunday's trip to Bolton. Clarke and Grant appeared to be working at cross purposes during the Fulham game.

Grant needs time and suggested the problems within the team, particularly in front of goal, had set in under Mourinho. "I would be worried if the problems started last week but if you remember before, against Rosenborg [in the Champions League], Blackburn and Aston Villa [in the Premier League], we didn't even create many chances," he said.

"I'm happy that we're at least creating more chances than in those games. It was a problem that was here before but I see that the players want to be positive. We have some problems but it's part of team life. We need to fix it.

"It's a long time until January, I will be with the players a lot more and I will get to know them better. In January, we will decide [about transfer activity]. If there are no injuries in the squad, I'm happy with it. I like the players' attitude."

Grant was publicly backed by the captain, John Terry. "The most important thing is that everyone - the fans, the players and the staff - give him their full support," he said. "As players, we will."